I'd be interested to know the basis of the "verticality" requirement... 1
part in 100 (about 1/2 degree) wouldn't appreciably change the loads at the
base (1% using the "small angle approximation"), and hopefully the design
isn't cutting it that close. (Assuming the guys are a reasonable distance
away from the tower.. all bets are off if the guy anchor is 10 feet from
the base of the tower...)
There's a "do the job right" aspect, of course, and the advice to set it up
now for inevitable adjustment later is certainly sound.
For a contractual document (i.e. you're hiring someone to put up a tower)
you need to provide "testable requirement". If standard industry practice
is that it's easy to get it vertical to 1 part in 400, then there's no
problem imposing that as a requirement.
However, if you're doing the work yourself, you're not necessarily
concerned about whether it meets some arbitrary standard, but more, whether
it's safe, and the "safe" requirement might be substantially looser than
the "pretty and good commercial practice" requirement.
Jim, W6RMK
At 07:01 PM 3/4/2003 -0500, KI7WX@aol.com wrote:
>A quick Google search reveals the following helpful post to TowerTalk back
>in Y2K. If memory serves, K7LXC has mentioned the 3" per 100 feet spec
>before on TT:
>
>
>
>6.2.2.1 plumb - For guyed structures, the maximum deviation from the true
>vertical shall be one part in 400, (3 in. per 100 ft).
>
>For self-supporting structures, the maximum deviation from true vertical
>shall be one part in 250, (4.8 in. per 100 ft).
>
>
>
>If it were my tower I'd try to get the tower a lot straighter than a foot
>off. I'd also adjust the positions of the preforms and turnbuckles now to
>allow easy tensioning and adjustment down the road.
>
>As written in the query he's just adjusting for plumb. Since this sounds
>like his first big tower you might remind him to adjust for appropriate
>guy wire tension too (Loos gauge, etc, etc).
>
>Hope that helps. I spent the better part of a morning adjusting the guy
>wires on my 55G tower to get it straight and pretensioned properly. Could
>have gone faster with some additional hands, but took my time, was patient
>and it went fine.
>
>Mark
>KI7WX
>_______________________________________________
>
>See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
>Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with
>any questions and ask for Sherman, W2FLA.
>
>_______________________________________________
>TowerTalk mailing list
>TowerTalk@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
|